Definition and Correlation Analysis of Power Quality Index of DC Distribution Network

Abstract

With the advantages of controllability, efficiency and flexible access to renewable energy, DC distribution network has become the development direction of distribution network at home and abroad. DC power quality is the core issue of its planning design and operation control, but the source and load fluctuations, diversity of disturbances and the sensitivity of power conversion equipment make it present new features. This article first analyzed the differences between AC and DC power quality, compares the AC power quality system, and defines the DC harmonics, voltage fluctuations and flicker, voltage sags, voltage unbalances, voltage deviations, etc. Due to the DC voltage characteristics and the special structure of the DC distribution network, there are obvious correlations between different DC power quality phenomena. This article analyzed the correlation between harmonics and fluctuations, deviations and stable unbalances, sags and transient imbalances. Finally, a typical case of DC distribution network was selected to analyze the mechanism of each power quality phenomenon under different operating conditions. Based on the quantitative relationship between the index definition and the relevant parameters, a model was built by Matlab/Simulink to verify the generation mechanism and the correlation of the indexs.